A tool holder must be able to prevent inadvertent withdrawal of the tool or bit from the holder and must also transmit, when desired, rotary motion to the tool or bit. In some applications, particularly those suitable for rotary hammers, the holder must permit the disengagement of the hammer or percussive action so that the tool or bit undergoes rotary movement only.
Problems associated with the retention and drive of the tool or bit have produced a number of proposed solutions.
In one such solution one set of members in the form of balls is used to retain the tool or bit and another set in the form of ridges is used to drive the latter. This necessitates the tool or bit having a shank with recesses to receive the separate sets of members.
In another such solution one set of cylindrically shaped members is used to retain and drive the tool or bit, and requires the tool or bit to have a shank of a configuration somewhat different from that required by the first solution referred to above.
Another arrangement described in British Pat. No. 896,189 has a single key like member to retain and drive the tool. However, there is no indication that this arrangement could accommodate tools with shanks of different configurations.
Due to the different requirements of many of the tool holders at present available, each is normally designed to accept a tool of one form only. An adaptor is required when a tool of another form is to be used.
It is therefore an object of this invention to provide a tool holder capable of more readily receiving tools with shanks of different configurations.
It is another object of this invention to provide for a rotary hammer a tool holder which automatically disengages the tool from percussive action of the rotary hammer when the tool is lifted from the work surface.
It is yet another object of this invention to provide a rotary hammer with an improved tool holder incorporating mode changing from hammer mode to rotary only mode.